Covered California officials say monthly premiums could rise by an average of 12.5 percent in 2018.

The program's executive director, Peter Lee, said about 3 percent of that is a direct result of uncertainty in Washington.

"We've just come out of a debate on the potential repeal and replace of the aca," said Lee.

All 11 existing insurers will continue providing coverage, but Anthem Blue Cross will reduce its 19 covered regions to three: Santa Clara County, the Central Valley and parts of Northern California.

A looming question is whether or not the federal government will continue making payments to insurance companies that help low-income consumers. If that doesn't happen, insurance companies would implement a surcharge on silver tier plans.

"This is a surcharge to cover the cost of helping 650,000 Californians get lower cost care," said Lee.

State officials said most customers would not feel the full impact and could shop for more affordable options.

In order to prevent the surcharge, California Insurance Commissioner Dave Jones threated to file suit if there is no action by Congress or the president.

"There will be continued uncertainty, until or unless the president agrees to fully fund the cautionary reduction payment that is necessary for millions of Americans and hundreds of thousands of Californians to afford their coverage," said Jones.

The 2018 projected increase is less than this year's 13 percent jump, and officials said consumers could see an increase of only three percent on average if they choose a more affordable plan.